The present invention relates to improvements in an automatic wire feeder of a wire electric discharge machine in which an electric discharge is generated between a traveling wire electrode and a workpiece so that the workpiece is machined by electric discharge energy.
FIG. 7 is an arrangement view showing an automatic wire feeder of a conventional wire electric discharge machine disclosed in Japanese Unexamined Patent Publication No. 2-224926. In the view, reference numeral 1 is a wire electrode, reference numeral 2 is a feed roller for giving a feed force to the wire electrode 1 in the case of automatic feed operation of the wire electrode 1, reference numeral 2a is a motor for driving the feed roller 2, reference numeral 3 is a pinch roller for pressing the wire electrode 1 to the feeder roller 2, reference numeral 4 is a first guide pipe, reference numeral 5 is a second guide pipe, capable of going up and down, for guiding the wire electrode 1 to the upper wire guide 6 when the second guide pipe goes down in the case of automatic feed operation of the wire electrode 1, reference numeral 7 is a cylinder block for elevating the second guide pipe 5 by air pressure, reference numerals 7a and 7b are inflow ports of air of the cylinder block 7, reference numeral 7c is air of high pressure, and reference numeral 8 is a jet nozzle for generating a water column to guide the wire electrode 1 which passes between the upper wire guide 6 and a lower wire guide not shown in the case of automatic feed operation of the wire electrode 1.
Next, operation will be explained below. A positional relation between the wire electrode 1 and each component of the automatic wire feeder before the start of automatic feed of the wire electrode 1 is shown in FIG. 7. Air 7c of high pressure (0.4 to 0.5 MPa) is made to flow into the cylinder block 7 from the inflow port 7a of air. An upper section of the second guide pipe 5 is formed into a piston. Therefore, the second guide pipe 5 is lowered to a position shown in FIG. 7 by the pressure of air 7c of high pressure. After the completion of this motion, the feed roller 2 is rotated by driving the motor 2a, so that the wire feeding can be started. As shown in FIG. 8, air 7c of high pressure for lowering the second guide pipe 5 flows from clearance (D in the drawing), which is formed between the first guide pipe 4 and the second guide pipe 5, into the second guide pipe 5, and the wire electrode 1 is vibrated by the air of high pressure flowing in this second guide pipe 5. While the wire electrode 1 is being vibrated as described above, the wire electrode 1 is guided by the second guide pipe 5 to the upper wire guide 6 shown in FIG. 7. In FIG. 7, after passing through the upper wire guide 6, the wire electrode 1 is guided by a water column formed by water jetted out from the jet nozzle 8 and passes through a machining start hole formed in a workpiece not shown in the drawing, so that the wire electrode 1 is guided to a lower guide not shown in the drawing. After passing through the lower wire guide, the wire electrode 1 arrives at a recovery roller not shown in the drawing. In this way, the automatic feed motion of feeding the wire electrode is completed.
Since the automatic wire feeder of the conventional wire electric discharge machine is composed as described above, a thrust is given to the wire electrode 1 by the torque generated by the feed roller in the process of the automatic feed motion of the wire electrode. That is, a current of air flowing from clearance (D shown in FIG. 8), which is formed between the first guide pipe 4 and the second guide pipe 5, into the second guide pipe 5 does not effectively contribute to an increase in the thrust to be given to the wire electrode.
In this structure, the following means is adopted. In order to reduce a frictional force generated between the wire electrode 1 and the first guide pipe 4 and also to reduce a frictional force generated between the wire electrode 1 and the second guide pipe 5 in the traveling passage of the wire electrode 1 so as to prevent the occurrence of buckling of the wire electrode, the wire electrode 1 is vibrated by higher pressure air 7c. For example, in the case where the diameter of the wire electrode is not more than 0.1 mm or in the case where a large curl is formed in the wire electrode, buckling of the wire electrode is caused in the guide pipe 5 or the upper wire guide section in some cases. Accordingly, in the conventional automatic wire feeder, it is impossible to ensure high reliability of automatic feed of the wire electrode.
Further, the guide pipe of the automatic wire feeder of the conventional wire electric discharge machine is composed of a double pipe structure including the first and the second guide pipe. Therefore, the mechanism is complicated, and further the guide pipe tends to be clogged by wire chips and wire pieces. Further, in the case where the guide pipe is clogged by wire chips, it is difficult to remove them. Accordingly, the conventional automatic wire feeder is disadvantageous in that the reliability of automatic feed of the wire electrode is lowered and further the maintenance cost is increased.
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide an automatic wire feeder of a wire electric discharge machine, the reliability of which is high, capable of suppressing an increase in the maintenance cost.
The present invention provides an automatic wire feeder of a wire electric discharge machine in which electric discharge is generated between a traveling wire electrode and a workpiece so as to machine the workpiece by the electric discharge energy, comprising: a feed roller for feeding the wire electrode; a slider block supported being capable of going up and down; a guide pipe, fixed to the slider block, for guiding the wire electrode; a hollow member, fixed to the slider block, the outer diameter of which is reduced in the wire feed direction; and a pressurized gas supply means for supplying pressurized gas toward the outer diameter of the hollow member, wherein a forward end section of the hollow member is inserted into an inner diameter section of an upper section of the guide pipe while a predetermined overlapping length is kept, a predetermined clearance is formed between the inner diameter of the guide pipe and the outer diameter of the forward end section of the hollow member, and a thrust is given to the wire electrode when pressurized gas, which is supplied by the pressurized gas supply means, flows in the guide pipe via the clearance.
In an automatic wire feeder of a wire electric discharge machine, the inner diameter of the upper section of the guide pipe is reduced in the wire feed direction.
In an automatic wire feeder of a wire electric discharge machine, the inner diameter portion of the hollow member is formed into a nozzle profile.
An automatic wire feeder of a wire electric discharge machine further comprises: a pressurized gas stopping means for stopping a current of pressurized gas flowing in the guide pipe at a forward end of the guide pipe, the pressurized gas stopping means capable of retracting from the wire traveling passage, wherein when it is necessary to wash the inside of the guide pipe, the passage of pressurized gas in the guide pipe is closed by the pressurized gas stopping means and pressurized gas is supplied from the pressurized gas supply means so as to wash the inside of the guide pipe.
In an automatic wire feeder of a wire electric discharge machine, a slit is formed at a forward end of the guide pipe.
In an automatic wire feeder of a wire electric discharge machine, the slit is formed in a direction substantially perpendicular to a plane on which a curl of the wire electrode is formed.
Since the present invention is composed as described above, the following effects can be provided.
In an automatic wire feeder of a wire electric discharge machine of the present invention, it is possible to automatically feed a wire electrode with high reliability by a conveyance force of pressurized gas flowing in a guide pipe.
Further, it is possible to conduct self-washing inside the guide pipe. Therefore, a wire can be automatically fed with higher reliability. Accordingly, the maintenance cost can be reduced.